CAIRO, Dec 12 (Reuters) - With a bust of Egypt's former
President Gamal Abdel Nasser in his office, opposition
politician Hamdeen Sabahy has a knack for the kind of rousing
rhetoric his nationalist hero employed to inspire the public.

The one-time student leader who founded the Popular Current,
a movement that has started to gain influence across the country
of 83 million, may be one of the biggest winners from a crisis
that has engulfed Islamist President Mohamed Mursi after he
expanded his powers and sparked nationwide protests.

Whether Sabahy or any other opposition figure can emerge as
a credible leader of those who reject Mursi and his fellow
Islamists may determine Egypt's future course.

"We will never differentiate in this nation between Muslim
and Christian, men and women, those in the countryside or in the
cities," Sabahy told a crowd this month in Tahrir Square where
protesters accuse Mursi of driving a wedge between Egyptians of
different faiths and opinions.

"In one hand" and "The people want to bring down the regime"
they chanted back at the leftist politician on the podium.

Egypt's disparate opposition, trounced in two elections by
well-organised Islamists since Hosni Mubarak was overthrown
almost two years ago, have been united by the latest crisis and
have proved that Mursi's Muslim Brotherhood and his allies do
not have a monopoly on mobilising Egyptians.

That is heartening to Christians, moderate Muslims and more
liberal-minded Egyptians angry at Mursi for pushing through a
constitution drafted by an assembly dominated by his Islamist
allies. It will go to a referendum on Saturday.

Sabahy, 58, sits alongside several other well-known
personalities in the opposition coalition, the National
Salvation Front, that was thrown together by the political
upheaval. Together they have brought tens of thousands onto the
streets, even if not quite as regularly as the Islamists have
done.

Like Sabahy, Nobel Peace Prize laureate Mohamed ElBaradei,
70, and Amr Moussa, 76, a former foreign minister under Mubarak
and then Arab League chief, have grown in standing.

But neither engenders the enthusiasm on the street that
greets Sabahy, who has said he rose from the son of a peasant to
his position now because of the policies of Nasser, who
enthralled Egyptians and Arabs in the 1950s and 1960s.

In another demonstration in Tahrir Square, the cauldron of
the anti-Mubarak uprising, ElBaradei addressed protesters this
month. But instead of the fluid and gesticulating performance of
Sabahy, the former head of the U.N. nuclear agency read his
message from notes, drawing muted cheers.

DIVISION

Moussa has won credit for actively engaging in the
constitution drafting process until withdrawing with others from
the assembly, but he still struggles to shake off his links to
Mubarak's discredited government.

"I ask for calm. Today we are in a situation that cannot
bear division," ElBaradei told a news conference by the Front
when Moussa, standing next to him, was accused by a heckler of
being a member of the "feloul", the derisive Arabic term
referring to remnants of Mubarak's order.

Yet there is still no clear figurehead that can claim the
mantle of leader of the opposition. Nor can any group whether
Sabahy's Popular Current movement or ElBaradei's Dostour
(Constitution) Party claim to speak for all opposition ranks.

The unity of these politicians for now is based on agreement
on what they oppose with little sign yet that the united front
will stretch much beyond that and to a common platform in
elections ahead.

"The lack of leadership is still a problem facing them,"
said Hassan Nafaa, a liberal-minded professor at Cairo
University, adding the Front "is mainly united by this crisis".

"Everybody understands there is a real danger facing all of
them, there is a risk that this constitution might lead to total
control of Muslim Brothers and their allies," he said.

On the street, opponents of Islamists praise the role of the
Front but fear opposition ranks will fragment as elections loom,
splitting their vote which damaged them in the parliamentary and
presidency races.

"The Front is standing with us in this crisis," said Ahmed
Mohamed, a 24-year-old banker protesting at the presidential
palace, whose walls were daubed with anti-Mursi graffiti.

"But when election time comes, I doubt they will run
together as they are so different and so far failed to come up
with a structure that shows who is the leader," he said.

The opposition has struggled to organise in the post-Mubarak
turmoil, and often been accused of relying too heavily on
well-known personalities rather than getting down to the more
gritty business of building a grass-roots network to get out the
vote.

MOBILISED

"The silent majority is mobilized now, but we don't know
whether those who rushed to the presidential palace will
recognise the united Front as their leader or are just mobilised
by hatred of the Muslim Brotherhood," said Professor Nafaa.

Opponents have struggled to reach many ordinary Egyptians
when faced with the social and charity network built up by the
Brotherhood over eight decades, even when the group was
repressed and hounded under Mubarak and his predecessors.

ElBaradei, a bespectacled and eloquent diplomat, who
returned to Egypt in 2010 from his home in Vienna where he ran
the International Atomic Energy Agency, had raised hopes in the
opposition that he would lead those against Mubarak's rule.

But critics say he never quite lived up to that billing,
although his party members have been prominent among protesters
in the crisis now, suggesting he is building a following.

ElBaradei pulled out of this year's presidential race saying
there was no point running when a constitution was not in place
to define the president's job. Detractors said it was because he
lacked a support base as he spent too much time abroad.

Sabahy and Moussa did run. But Moussa, widely praised when
head of the Arab League for his tirades against Israel and seen
as a front-runner early in the race, found his vote cratered on
election day. That was largely blamed on his struggle to
convince Egyptians he marked a real break with the past.

Sabahy, however, was one of the biggest surprises, coming
from behind to reach third place and narrowly missing a run-off.
Some analysts say that good showing was partly because he was
the only prominent candidate who was not from the Islamist camp
and had no links to Mubarak's rule.

He said the Front could presage a more united approach in
the parliamentary vote. "There is an agreement over a national
Egyptian project that no one should dominate or be excluded
from," he said at his movement's headquarters.

Showing a popular touch, he criticised the draft
constitution he said was polarising the nation but also laid
into Mursi's tax rises, that the president implemented and then
withdrew within hours because of a public backlash.

"What Mursi did was a big shock to a large sector of the
public," he said.

Yet, while the Front may have raised the profile of
opposition leaders questions remain about how rivals of Mursi
and his Islamist allies will maintain cooperation seen as vital
if they are really to challenge Islamists in future votes.

"The National Salvation Front can't be anything more than it
already is," said Shadi Hamid of the Brookings Doha Centre. "It
is not going to be an institutionalised movement because the
three leading figures don't agree on that much."

Hamid said liberal politicians needed to move beyond the
personality politics. Although Sabahy's Popular Current was
building a broader base, Hamid said the leftist had yet to show
he could fight an election "that goes beyond fiery speeches and
the figure of Hamdeen Sabahy."